Sen. Charles E. Schumer, D-N.Y., said the debate on comprehensive immigration overhaul legislation could take three to four weeks once it hits the Senate floor.

“I think it could take three, four weeks,” Schumer, the third-most-senior Senate Democrat, said at a Politico Playbook breakfast Wednesday.

“This is such an important issue to America and it’s so complicated ... that I think we should have a full and robust debate,” Schumer continued. “The hope is that we can pass this with a nice sizable bipartisan majority because that would ... make it easier for the House to pass it. We don’t want to have just four Republicans.”

Schumer is working with a bipartisan group of seven other senators, including John McCain, R-Ariz., who is taking the lead to try to draft a bill that can be marked up by the Judiciary Committee and passed by the Senate in the late spring.

McCain, who also appeared at the breakfast, said the group’s goal is to snag about 80 votes, given that some people on both sides of the issue are not likely to be won over to support a centrist package.

“We have got to maintain the center,” McCain said. “There will be people on at both ends [of the political spectrum] that will not ever agree. We have to understand that we are not seeking 100 votes, but we are seeking 80 votes.”

“That’s the hope, but getting a large majority on both sides is very important.” Schumer said.

McCain expects the group to vote together during consideration of the bill to keep any “poison pill” amendments from being attached.

“I think we have to,” McCain said. “It’s going to be fragile, as these kinds of things are. We are going to take some tough votes to keep it intact, but that is so far down the road right now ... we haven’t talked about it.”

Schumer said he doesn’t expect he and McCain to agree on every amendment that will receive a vote but “the core principles we came up with must stay intact.”

Those principles, which were unveiled Monday, include establishing a path to citizenship for those currently in the country illegally, overhauling the current immigration system, reducing the hiring of undocumented workers and creating a guest worker program. The group of eight will meet on Tuesday and Thursday, and staff will meet Wednesday to draft their proposal.

“We alternate because we don’t want it to be a Democratic proposal or a Republican proposal, so we alternate between John’s office and my office,” Schumer said.

“Last night we started measuring some of the biggest issues. The parameters for measuring when the border is secure and how to deal with the 11 million to gain citizenship, given that there are so many and our colleagues want to make sure that they are not treated any better having crossed the border illegally than people who waited in line,” Schumer said. “We made huge progress.”

McCain said it’s important that Sen. Marco Rubio, R-Fla., is part of this effort.

“I think it’s important and I think it’s helpful,” McCain said. “Marco Rubio represents a very large state with a lot of Latino voters.”

“His family came from Cuba and he understand the issues confronting people who came to this country legally or illegally as well as anyone,” he said.

Asked if it would help Rubio, who may have aspirations to run for president in 2016, politically, McCain said, “What I’ve found in my political life, if you do the right thing it always ends up OK. If you do something for political reasons, in my experience, and I have done that, it’s turned out badly,” McCain said, who ran a failed campaign for president in 2008. “So, I think that Marco Rubio is doing the right thing.”